Solazyme, a South San Francisco startup that makes algae-based biofuel, raised nearly $200 million in its initial public offering. From an opening price of $18 a share, the stock finished on the Nasdaq exchange at $20.71 with a 15 percent gain.

Solazyme was the first biofuel company of its kind to test the IPO waters — and the third high-profile tech debut of the past seven days.

“I think there’s a lot of appetite in the general market for growth stocks,” said David Cheng, director of research at the Cleantech Group in San Francisco.

Russian search engine Yandex raised $1.3 billion in Monday’s debut on the Nasdaq and closed Friday at $34.45, up 38 percent from where it priced. Meanwhile, Mountain View social network LinkedIn continues to see steady demand for its shares, which closed at $88 a week after its IPO.

Solazyme’s $18 offering price reflected investor appetite leading up to Friday’s IPO; it had previously announced it would sell the stock at a range of $15 to $17. Nearly 11 million shares of the company’s common stock were offered under the ticker symbol SZYM.

Friday’s closing price gives Solazyme an estimated market value of $1.2 billion. Investors in the company include the Roda Group of Berkeley, Braemar Energy Ventures, Lightspeed Venture Partners and entrepreneur Richard Branson.

The company — founded in a Palo Alto garage in 2003 — grows algae in fermentation tanks and extracts the oils for a range of applications. It has signed contracts with everyone from the U.S. Navy, which is testing Solazyme’s fuel in military vessels, to Sephora, a high-end cosmetics chain that carries Solazyme’s algae-based skin care line.

In addition, Qantas Airways reportedly plans to buy up to 100 million gallons of Solazyme’s jet fuel a year. And the company has been awarded $21.8 million from the Department of Energy to build a biofuels refinery in Pennsylvania.

Solazyme’s IPO prospectus says its technology “transforms a range of low-cost, plant-based sugars” into oils that can replace those traditionally derived from petroleum, plants and animal fats.

“Algae is promising on several fronts,” said Blake Simmons, deputy director of Sandia National Laboratories. “Algae can be grown on land that you can’t grow food on, and it can be a platform for a lot of different products. The challenge is, how do you make it cost-competitive with conventional fuels?”

Competitors include Emeryville-based Amyris, which makes a sugarcane-based biofuel, and Gevo of Colorado. Both companies have gone public in the past year and have enjoyed steady share-price growth. “The market’s recognizing there’s an opportunity for these companies to grow into huge biofuels companies, but they’re paying the bills by going into biomaterials” such as cosmetics, Cheng said.

King Lip, chief investment officer for San Francisco’s Baker Avenue Asset Management, agreed that Solazyme’s debut reflects “that it’s still very much a ‘risk-on’ type of market.”

As for whether tech’s IPO charge will continue, Lip said that largely depends on the industry. “Social networking, yes; semiconductors, probably not as great,” he said.

Indeed, Freescale Semiconductor Holdings, based in Austin, priced this week below its expected range of $22-24 and closed Friday at $18.65.

Even within green technology, there are varying degrees of investor appetite, Lip and Cheng both said. “For instance,” Lip noted, “solar companies this year really haven’t done that well.”

Venture capital firms continue to pour money into cleantech, with $1 billion invested in the first quarter of this year. Observers have predicted such deals will continue based on the growing global demand for energy and concerns about the sustainability and environmental impact of fossil fuels.

Still, of the 125 companies in Ernst & Young’s IPO pipeline at the end of the first quarter, just one — Massachusetts-based Bruker Energy & Supercon — is classified as cleantech.

With Monday’s Memorial Day holiday looming, the only U.S. IPO expected next week is that of Sabre Industries, a Pennsylvania provider of transmission towers and other wireless equipment.

A transit village with apartments, retailers, restaurants and a hotel is rising in Milpitas next to The Great Mall, close to light rail and the under-construction BART station. It’s one of several Silicon Valley projects sprouting up near transit.